Patricia A. McIntyre

Binding of trace amounts of ionic indium-113m to plasma transferrin

When indium-113m was injected intravenously in ionic form for blood pool scanning, it was bound to plasma transferrin. In vitro studies utilizing starch gel electrophoresis and immunoelectrophoresis showed that trace amounts of indium were bound almost entirely to the transferrin; iron-59 labeled plasma was used for comparison. Starch gel electrophoresis and gel filtration were carried out with plasma samples containing increasing amounts of indium. It appeared that approximately 4 μg of indium per ml of normal human plasma saturated the transferrin and the excess indium above this level was bound mainly to α2-globulins.

The effect of volume on the distribution of substances instilled into the peritoneal cavity

Abstract 99m Tc-labeled human serum albumin was placed into the peritoneal cavity of monkeys with 20- and 250-ml volumes of vehicle. Its distribution was monitored with a γ camera. Only the large volume injections produced uniform distribution of the label.

Surface sulphydryl groups and phagocytosis-associated oxidative metabolic changes in human polymorphonuclear leucocytes.

Summary. The role of surface sulphydryl (‐SH) groups of human polymorphonuclear leucocytes on phagocytosis and. phagocytosis‐associated oxidative metabolic changes was studied. p‐Chloromercurybenzene sulphonic acid, a surface ‐SH group inhibitor, had no effect on phagocytosis, superoxide production during phagocytosis, or killing of S. aureus by the leucocytes, while it inhibited phagocytosis‐associated stimulation of hexose monophosphate pathway activity and H2O2 production. In contrast, N‐ethylmaleimide, which inhibits both intracellular and surface ‐SH groups, inhibited phagocytosis and phagocytosis‐associated oxidative metabolic changes. p‐Chloromercurybenzene sulphonic acid also inhibited the stimulation of hexose monophosphate path‐way activity by exogenous H2O2, suggesting a regulatory role of plasma membrane on the pathways activity in human polymorphonuclear leucocytes. The results also suggest that: (1) superoxide production is the primary event of oxidative metabolic changes during phagocytosis, (2) superoxide plays an important role in the killing of S. aureus, and (3) the hexose monophosphate pathway plays a primary role in producing NADPH for H2O2 production from superoxide.

Kinetics and Distribution of 111Indium-Labeled Platelets in Patients with Homocystinuria

Homocystinuria is an inborn error of metabolism involving a high incidence of thromboembolism. It sometimes improves with large doses of pyridoxine. We investigated the kinetics and distribution of 111Indoxine-labeled platelets in 11 normal volunteers and 12 patients with homocystinuria, none of whom had clinical evidence of acute thrombosis at the time of the study. Six of the patients were resistant to pyridoxine and had homocystinemia. There were no statistical differences in mean platelet-survival times between pyridoxine responders and nonresponders or between normal subjects and pyridoxine responders or nonresponders, regardless of whether a linear, exponential, or multiple-hit model was used to analyze the kinetic data. Plasma homocystine levels had no apparent effect on mean platelet-survival time. There was no abnormal accumulation of platelets in any of the patients, and the distribution of platelets in liver and spleen was similar to that in normal subjects. Our results suggest that the kinetics and distribution of platelets in patients with homocystinuria who have no clinical evidence of thromboembolism are normal. Thus, the data do not provide evidence for disordered platelet function or for an ongoing interaction of platelets with vessel walls in this condition.

Placental transport of vitamin B12 in the pregnant rat

Placental transport of vitamin B(12) was studied in the pregnant rat in two series of experiments. In the first series animals were given cyanocobalamin-(57)Co intravenously at various stages of gestation. High specific activity tracer was used and doses of B(12) were 1-2 ng per animal. The rats were killed from 15 min to 24 hr after injection and the fetuses, placentas, and serum were assayed for radioactivity. In the second series using uninjected animals, absolute amounts of vitamin B(12) in fetuses and placentas were measured at stages of gestation from day 12 through day 20. There was a progressive increase in B(12) transferred to the fetus during gestation. Although the quantity of vitamin B(12) transported per 24 hr was proportional to fetal weight, the amount transported per gram of placenta increased tenfold from day 10 through day 19. Uptake of tracer B(12) by placenta was initially rapid; however, no radioactivity appeared in the fetus until 2 hr after injection. The actual amount of B(12) in placenta increased throughout gestation, and the placental concentration of B(12) was greater than maternal plasma and fetal tissue concentrations at all times measured. These data suggest that the ability of placenta to transport B(12) increased throughout gestation, and that the rate-limiting step in the transport process was either the passage of B(12) from the maternal to the fetal side of placenta or the transfer from placenta into fetal plasma.

Stimulation by propylthiouracil of the hexose monophosphate shunt in human polymorphonuclear leucocytes during phagocytosis.

The effect of propylthiouracil on glucose metabolism in human polymorphonuclear leucocytes was studied. At a therapeutically achievable concentration (0.1 mm), propylthiouracil stimulated hexose monophosphate shunt activity in normal leucocytes during phagocytosis but not in resting cells. However, in the presence of hydrogen peroxide it stimulated hexose monophosphate shunt activity in resting cells, and in the soluble fraction when reduced glutathione and reduced nictotinamide adenine dinucleotide phosphate (NADPH) were also present. Propylthiouracil had no effect on glucose‐1‐C oxidation in either phagocytosing or resting leucocytes obtained from two male patients with chronic granulomatous disease. Stimulation of the hexose monophosphate shunt activity in normal leucocytes during phagocytosis also was demonstrated with methimazole, thiouracil and thiourea, but not with adenine, uracil or urea. There was an apparent minimal common structure requirement in thiourea. Propylthiouracil had no effect on phagocytosis, formate oxidation, glucose‐6‐phosphate dehydrogenase, 6‐phosphogluconate dehydrogenase or catalase activities. Thus, the stimulation of the hexose monophosphate shunt activity by propylthiouracil is dependent on hydrogen peroxide and is best explained by its stimulation or participation in the glutathione cycle.

Functional development of phagocytic activityof the spleen

The improvement of phagocytic activity of organs was studied in rats by means of 99mTc sulfur colloid uptake. This function was measured in the newborn rat, 1-, 2-, 3-, and 4-week-old baby rats and in adult rats. Organ distribution of the 99mTc-S-colloid showed marked phagocytic activity of the liver in all age groups including the newborn period. Phagocytosis in bone marrow was markedly increased and that in spleen markedly decreased at the time of birth. However, rapid improvement of phagocytic activity with age was prominent in the spleen.

Treatment of megaloblastic anemias

Abstract Megaloblastic anemia is almost always the consequence of a deficiency state. The proper management of this disorder requires the identification of the nature of the underlying abnormality, since this dictates the choice of the specific therapeutic agent for the deficiency, the duration of treatment required, and the other therapeutic measures which may be necessary.

Use of radioisotope techniques in the clinical evaluation of patients with megaloblastic anemia

Because virtually all cases of vitamin B12 deficiency seen in this country are due to malabsorption, the availability of radioactive vitamin B12 for direct measurement of absorption of this essential nutrient has proved to be of great clinical value. These tests are useful not only in demonstrating vitamin B12 malabsorption but also often in defining the pathophysiological mechanism responsible for this abnormality. The urinary excretion test of Schilling remains the most useful test for vitamin B12 absorption. Minor precautions and modifications in technique make the test results more reliable and easier to interpret. The 8-hr plasma test for vitamin B12 absorption can no longer be considered acceptable. Some patients with vitamin B12 malabsorption have results in the normal range when studied by this method. Serum vitamin B12 assays utilizing radioactive vitamin B12 and the isotope dilution principle are not widely used and are useful screening tests. Low normal or borderline results observed in patients with clinical evidence suggestive of vitamin B12 deficiency should be interpreted with caution or confirmed by radioactive vitamin B12 absorption studies. Radioactive vitamin B12 can also be used for rapid, reliable assay of gastric intrinsic factor, antibody to intrinsic factor and unsaturated vitamin B12 serum. Methods using radioactive folate compounds for similar in vivo and in vitro studies are not yet applicable for routine use in nuclear medicine laboratories.

Neuronal ceroid-lipofuscinosis. Studies of granulocyte enzyme activities.

Neuronal ceroid-lipofuscinosis is characterized by pigmentary degeneration of the retina, psychomotor degeneration, epilepsy and intracellular deposition of ceroidlipofuscin. Recent reports have suggested that deficiency of peroxidase is the basic genetic defect. However, deficiency of myeloperoxidase could be demonstrated in some but not all patients; this deficiency was noted only when p-phenylenediamine (PPD) was used as hydrogen donor and could not be confirmed with guaiacol. We found that horseradish peroxidase (HR-P) oxidized PPD in the absence of added H2O2. The oxidative product of PPD showed the same absorption spectrum as the peroxidative product. The oxidation of PPD by HR-P was not inhibited by catalase or superoxide dismutase. In addition, catalase oxidized PPD in the presence of H2O2. Soluble and granular fractions obtained from human polymorphonuclear leukocytes (PMN) also oxidized PPD in the absence of H2O2. Addition of H2O2 inhibited the oxidation of PPD in some cell fractions. This inhibition could be partially eliminated by dialysis of the cell fractions. Thus, PPD is not a suitable hydrogen donor for the study of peroxidase. This may explain the variable results obtained by the previous investigators. In contrast, guaiacol did not show these undesirable characteristics. The PMN peroxidase (measured with guaiacol), catalase, beta-glucuronidase, acid and alkaline phosphatases were studied in individuals from three families with juvenile neuronal ceroid-lipofuscinosis. Family 1: an affected boy and healthy parents; all showed normal enzyme activities in both soluble and granular fractions. Family 2: two affected sisters, one healthy sib and mother, and Family 3: one affected boy; all showed reduced peroxidase activities in the granular fractions. Other enzymes were normal. The role of peroxidase deficiency in the pathogenesis of neuronal ceroid-lipofuscinosis is not clear. The basic defect of this syndrome remains uncertain.